strip trailing newlines on incoming data

some clients send a newline at the end of each metric, using it
as a terminator rather than a delimiter; cope with it
handle multimetric transmissions

a transmission consists of one or more metrics separated by
newlines; see https://github.com/b/statsd_spec

With this patch, pystatsd should handle incoming transmissions
that provide more than one metric at once.
look for counters as such, warn on unknown types
correct a log message
delete, do not clear, flushed timers

They are already reinitialized as needed, and deleting them leaves
the system primed for an IndexError:

  File ".../py-statsd/pystatsd/server.py", line 111, in process
      self.timers[key][0].append(float(fields[0] or 0))

...because there will be no [0] in the timer.  Fortunately, timer
lists are initialized as needed, so deleting this seems to make
everything do the right thing.
when logging sent gauge, call values "values" not "counts"
fully clear gauges and counters after sending

Without this commit, counters and gauges that have been seen before
will be sent over and over, each differently.

Counters will be reset to 0 after their sending, and will send that
zero over and over.  Gauges will not reset at all, and will send
their new value repeatedly.

To confirm that this is currently the case, I changed the debug
output to include the timestamp:

    print "Sending %s => count=%s @ %s" % (k, v, ts)

After sending a counter and gauge only once each:

    Sending foo-counter => count=0.1 @ 1371864200
    Sending foo-gauge => count=123.0 @ 1371864200

    [ …10s go by… ]

    Sending foo-counter => count=0.0 @ 1371864210
    Sending foo-gauge => count=123.0 @ 1371864210
Merge pull request #69 from rjbs/multimetric-process

fix timer handling, handle multimetric transmissions
Merge pull request #70 from rjbs/debug-clarification

when logging sent gauge, call values "values" not "counts"
Merge pull request #71 from rjbs/reset-harder

fully clear gauges and counters after sending
add gauge example to read me
version bump
refactor the main "process" function for pystatsd

* Eliminate bogus metrics right up front.  Warn and drop them.
* Rename variables: data, fields, bits, bit... lots of overly
  generic names.  Instead, produce four clear variables: key, value,
  mtype, and rest.
* Break the big if/else's clauses into distinct functions to be
  easier to read on their own.
* Avoid some type mismatches.  Previously, an Int could end up in
  what would otherwise be a List of Str.